As new processes for drilling, completion, production, hydrocarbon enhancement, and reservoir management are developed, advancements in technologies related to temperature, pressure, and flow monitoring and downhole device control are required. Reservoir development systems must be constantly monitored to ensure maximum production. For example, with gravel-packed production systems, perforations become clogged over time, so that optimum flow rates are not maintained. To restore the production of the well, it has heretofore been a common practice to pull the entire length of production tubing out of the casing to clear the obstructed tubing perforations, or replace the perforated tubing section, and then re-install the production tubing within the casing. This task is laborious, time-consuming and expensive. Thus, to ensure more efficient production and prevent clogs or blockages, downhole monitor and control systems have been developed. Similar issues arise from artificial lift optimization, reservoir pressure monitoring, etc.
In some systems, surface controllers are hardwired to downhole sensors which transmit information to the surface. For example, wire line production logging tools are used to provide downhole data on pressure, temperature, flow, gamma ray and pulse neutron using a wire line surface unit. The data is processed by surface computer equipment and control signals are then transmitted back down the same wire or an alternative wire to manipulate the operating configuration of the system downhole.
Other downhole control systems use a remote computer control system with microprocessor controllers, electromechanical control devices and sensors. The microprocessor controllers transmit control signals only upon actuation by receipt of an actuation signal from an outside source, such as a surface transmitter.
Downhole control systems interface with surface control systems by both wireless and hardwired transmission mediums. Wireless acoustic signals are transmitted down a tubing string, such as production pipe or coiled tubing. Acoustic transmission is also done through the casing stream, electrical line, slick line, subterranean soil around the well, tubing fluid and annulus fluid. Acoustic transmitters and receivers are well known.
Acoustic downhole control systems require a solid mechanical connection between the transducer and the transmission medium. Thus, acoustic downhole control systems are permanently installed into the downhole apparatus to enable good communication between the acoustic transmitter and the acoustic transmission medium.
A known system for monitoring a formation surrounding a borehole in a production well includes a formation evaluation sensor permanently located downhole in a production well having at least two boreholes, wherein at least one of the boreholes is a branch borehole, the sensor sensing a formation parameter which is not normally present within the borehole. Automatic control is initiated downhole without an initial control signal from the surface or from some other external source. The system has downhole sensors, downhole electromechanical devices, and downhole computerized control electronics whereby the control electronics automatically control the electromechanical devices based on input from the downhole sensors.
The system has sensors which monitor a variety of actual downhole condition parameters, such as pressure, temperature, flow, gas influx, etc. The system is also preprogrammed to determine whether the actual condition parameters fall within an acceptable or optimal range. When the actual environmental conditions fall outside the acceptable or optimal range, the system is preprogrammed to operate a sliding sleeve, shut off device, valve, variable choke, penetrator, perf valve or gas lift tool. The system has a remote power source and operates independently of any control from the surface. Thus, the only way to change the systems operating parameters, is to pull the entire production apparatus, completion system, or drilling apparatus with the incorporated control system from the wellbore, reconfigure the control system, and reinsert the entire apparatus back into the wellbore.
Permanent downhole systems may only be modified, reconfigured or serviced by pulling the entire downhole apparatus out of the wellbore. As noted above, it is laborious, time-consuming and expensive to pull the entire length of production tubing out of the casing to service and re-install a downhole control system. Further, once a permanent downhole control system is installed in a wellbore, the control system is fixed and operates from only one location during the entire time that the production system is in the wellbore. In some applications it is desirable to operate the control system at various locations and for shorter periods of time relative to the life of the entire production system.